With global warming grabbing headlines, carbon-free nuclear power is gaining popularity—and with it, concerns over what to do with the spent uranium fuel. The largest long-term burial project, Yucca Mountain, has stalled, and even though uranium’s first trip through a reactor extracts only 5 percent of its energy, power plants in the U.S. don’t reprocess fuel. This is mainly because the most common form of uranium, an ion called uranyl, is extremely difficult to extract from the spent fuel rods. But a new Pac-Man-like molecule could change that.